In the typical wire-line operation, a metal cable or wire-line is used to suspend and control various tools where the tools are to be employed below the surface of the earth within the interior of the well. When the tool is occasionally brought up too quickly or is, for whatever reason, severed or separated from the wire line, the tool catch operates to catch the separated tool and there by prevent its loss down hole. In particular, the tool catch is useful in preventing tool loss as a result of a broken line while performing swabbing operations.
Swabbing is a form of “well control” that releases bottom hole pressure in an oil well in order to “kick” the well off. After wells are first drilled, they are usually fractured by a pressurized liquid to help open up “production zones” where oil or gas can travel to from the surrounding vicinity of the well.
Swabbing rigs are used to remove the fluids from the production zones. These swabbing rigs normally have a winch with a cable and a foldable mast with a pulley on top. First, a swabbing rig operator must back the rig as close to the well as possible. Next, the operator raises the mast and moves it until it is aligned with the center of the well. Next, the operator lowers swabbing tools attached to a cable in and out of the well casing via a “winch drum”. Here, the operator must be able to maintain control of the machine while taking into account the well's sound and depth.
The activities of the swabbing rig then allow for the removal of the liquids inside the well. Standard practice, with respect to a typical well, involves removing six or so barrels of fluid out of the well. This practice is referred to as a “run”. Some wells may take just one run while other may require multiple runs. Removing these fluids then causes the bottom hole pressure to increase. This allows the oil or gas to be pushed out of the well to cause it to start “flowing”. Oilfield workers may then start collecting and storing the natural resource that is being emitted from the well. As the well ages, the bottom pressure of the well may fall below the level required to push oil and gas out of the well. As a result of insufficient pressure, the well stops flowing and the swabbing process needs to be performed to restore favorable conditions for the well to operate.
When the swabbing tool is raised, a “crown-out” situation can occur where the swabbing tool is pulled too high or the line is damaged. Crown-out can cause the cable attached to the tool to break and as a consequence, the swabbing tool can drop into the well. Crown-out can occur when the operator of the rig is unsure of the position of the tool. While the cable typically includes markers to warn the rig operator when the tool is near the surface, for various reasons, such as operator inattention, or defective or poorly maintained equipment, tools can become detached and are dropped. Retrieving the dropped tool can be difficult, time consuming and expensive. Any amount of time that the well is not producing is costly.